1. Technical Field
This invention relates to voltage detection device and system.
2. Related Art
A known battery control device, as disclosed in Japanese Patent Application Publication No. 2003-92840, includes fault diagnosis means for detecting a spontaneous change in threshold for overcharge and/or over-discharge detection of a battery cell. More specifically, the battery control device of Japanese Patent Application Publication No. 2003-92840 is configured to detect a cell voltage of the battery cell and compare the detected cell voltage with the threshold.
In the above device, the threshold is forcibly shifted from a normal value by a given amount when the cell voltage of the battery cell is compared with the threshold. That is, the threshold is incremented or decremented by the given amount. In case the forced change in threshold doesn't reverse a relation between the cell voltage of the battery cell and the threshold in terms of the magnitude of voltage, the battery control device determines that the spontaneous change in threshold is large. This allows a threshold characteristic deviation of a voltage detector in the device to be detected.
In the above device, however, since an analog-to-digital (AD) converter included in the voltage detector, which outputs a signal including one bit information indicative of whether or not the detected cell voltage of the battery cell is above the threshold, is considered to be of one-bit type, only characteristics of the voltage detector including the AD converter can be diagnosed.
In general, in an analog-to-digital (AD) conversion circuit of such a device as described above, a multiplexer switches between a plurality of battery cells to be connected to the AD converter. In such configuration, it may be assumed that there exists a switch selector that controls switching operation of the multiplexer.
Conventionally, even in the presence of a fault (or abnormality) in the switch selector, cell voltages of the battery cells remain unchanged. In other words, the fault in the switch selector doesn't affect the cell voltages of the battery cells. Therefore, it is unable to self-diagnose the switch selector on the basis of the detected cell voltages of the battery cells.
In consideration of the foregoing, exemplary embodiments of the present invention are directed to providing voltage detection device and system that are capable of self-diagnosing the switch selector for controlling switching operation of the multiplexer.